1. Field of the Invention
The recovery of heat, especially moderate temperature level waste heat, from a gas stream containing fouling and/or corrosive constituents.
2. Description of the Prior Art
The recovery of low level previously wasted heat from sources such as flue gas has received attention in recent years because of the energy crisis. The cost of conventional fuels such as oil, coal and especially natural gas has escalated to the point where it is now profitable to install ancillary heat recovery units to recover previously wasted heat contained in plant effluents such as flue gas. The problem of efficiently and usably recovering such heat is compounded by the fact that it is only available at a relatively low temperature level, and in the case of flue gas the sensible and latent heat contained in the gas must be recovered from a large quantity of gas having low heat content. Flue gas produced by burning sulfur containing fuels is of an extremely corrosive nature, especially when the flue gas is scrubbed by aqueous media which generates sulfurous and sulfuric acids in situ. Flue gas usually also has a substantial particulate loading, e.g., dust, soot, fly ash, etc.
Heat recovery schemes of various types are shown in U.S. Pat. Nos. 1,083,885; 1,986,529; 2,090,466; 2,878,099; 3,169,575; 3,439,724 and 3,906,507.